Hereinafter, an acceleration sensor, one of conventional inertia force sensors, will be described with reference to the technique disclosed in Patent Publication 1.
FIG. 15 is a top view illustrating a detection element of a conventional acceleration sensor disclosed in Patent Publication 1. FIG. 16 is a cross-sectional view of the detection element taken along the line 16-16. FIG. 17 is a cross-sectional view of the detection element taken along the line 17-17.
In FIG. 15 to FIG. 17, the conventional acceleration sensor includes: detection element 51 for detecting acceleration; and a processing circuit (not shown) for subjecting an acceleration signal outputted from detection element 51 to an arithmetic processing to detect acceleration. Detection element 51 has: support section 54 supporting weight section 52; and fixation section 58 connected to support section 54 via flexible section 56. By fixation section 58, detection element 51 is mounted on mounting substrate.
Flexible section 56 has an arm-like shape. Flexible sections 56 are provided to draw a cross shape having the center at support section 54. A pair of flexible sections 56 and support section 54 are provided on a single straight line.
Flexible section 56 has distortion resistance element 60. Based on a change in the status of flexible section 56 deflected due to the movability of weight section 52, a change in the resistance value of distortion resistance element 60 is outputted as an acceleration signal.
Next, the following section will describe the detection of acceleration using detection element 51.
In an X axis, a Y axis, and a Z axis orthogonal to one another, when arm-like flexible sections 56 forming a cross shape is provided in the X axis direction and the Y axis direction and when acceleration is generated in the X axis direction for example, this causes weight section 52 to move in the axial direction along which acceleration is generated. This causes weight section 52 to rotate around support section 54 in the Y axis direction and flexible section 56 is deflected. As a result, among flexible sections 56 provided in the X axis direction, one flexible section 56 is deflected in the positive direction of the Z axis and the other flexible section 56 is deflected in the negative direction of the Z axis. Then, two distortion resistance elements 60 provided in two flexible sections 56 are also deflected in the positive and negative directions of the Z axis in accordance with the deflection of flexible section 56, thus causing a change in the resistance value of distortion resistance element 60. This change in the resistance value is outputted as an acceleration signal to detect acceleration.
By designing the acceleration sensor as described above based on a detection axis along which acceleration is desired to be detected, the acceleration sensor is used for a posture control apparatus and a navigation apparatus of a movable body such as a vehicle.
In the case of the above conventional detection element however, when acceleration is generated in the X axis direction for example in FIG. 15, this causes weight section 52 to move around Y axis in X axis direction. However, the move of weight section 52 is limited by flexible section 56 provided in X axis direction. Specifically, although weight section 52 is caused to rotate around support section 54 in the Y axis and thus flexible section 56 is deflected, the limitation by flexible section 56 causes this deflection amount to be small and thus a change in the resistance value of distortion resistance element 60 is also small to thereby cause a low detection sensitivity, which is disadvantageous.
Next, an angular velocity sensor is generally structured so that a detection element of various shapes (e.g., tuning fork-like shape, H-like shape, or T-like shape) is caused to vibrate to electrically sense the distortion of the detection element due to the generation of Coriolis force to thereby detect an angular velocity.
For example, Patent Publication 2 discloses an angular velocity sensor that has an oscillator having a tuning fork-like shape. This angular velocity sensor is structured so that detection electrodes are provided at an inner side face and an outer side face of two tuning fork arms constituting the tuning fork oscillator and driving electrodes are provided at surfaces of both of the tuning fork arms.
This angular velocity sensor is structured so that a signal supplied to the driving electrodes from a driving power source gives resonant oscillation to the tuning fork oscillator. When an angular velocity is applied in this status, the tuning fork arms are deflected in a vertical direction to the vibration direction based on the Coriolis principle. As a result, the detection electrode outputs an angular velocity signal in accordance with the level of the deflection.
As in the acceleration sensor, the angular velocity sensor as described above is also used, in accordance with the detection axis along which a detection axis along which acceleration is desired to be detected, for a posture control apparatus and a navigation apparatus of a movable body such as a vehicle.
Conventionally, when the acceleration sensor and the angular velocity sensor as described above were installed in various electronic devices, an exclusive angular velocity sensor was used to detect an angular velocity and an exclusive acceleration sensor was used to detect acceleration.
Due to this reason, when both of an angular velocity and acceleration are to be detected in a combined manner in various electronic devices, a plurality of angular velocity sensors and acceleration sensors were mounted on the mounting substrate of the electronic device, respectively.
This conventional configuration has required, in accordance with the detection axes of an angular velocity and acceleration to be detected, angular velocity sensors and acceleration sensors to be mounted on the mounting substrate, which disadvantageously requires a large mounting area.    [Patent Publication 1] Japanese Patent Unexamined Publication No. H10-48243    [Patent Publication 2] Japanese Patent Unexamined Publication No. 2001-208546